How to get nested relationship entities with nested subqueries SQL? - sql

Question

I have these 4 tables: Scorecard, Section, Topic, Answer.
Each scorecard can have many sections. Each Section can have many topics and each Topic can have many answers.
I am looking to retrieve the data in the following form. Get all sections where scorecard id is equal to to a certain id i do this by left joining and it works so far. Then for each section I want to get of all it's topics and answers as well.
=> Expected Output
[{section1,
topics:[{topicName, answers:[{answerName}]}]},
{section2,
topics:[{topicName, answers:[{answerName}]}]}]
I made adjustments to my query and joint the tables correctly but the output data is not correctly organized as I was It to be.
Query:
SELECT sec."id",
sec."name" AS "sectionName",
to_json(topics) as "topics"
FROM "scorecard" sc
LEFT JOIN "section" sec ON sc."id" = sec."scorecardId"
LEFT JOIN (SELECT tp.*, to_json(answers.*) as "answers"
FROM "topic" tp
LEFT JOIN (SELECT ans."name" as "answerName", ans."topicId"
FROM "answer" ans) answers ON answers."topicId" = tp."id"
) topics
ON topics."sectionId" = sec."id"
WHERE sc."id" = $1
The current output:
[ id: 85,
sectionName: 'Consultation',
topics: {
id: 109,
name: 'Was the information correct?',
answers: [{ answerName: 'Yes', topicId: 109 }, answers: { answerName: 'NO', topicId: 109 }
]
},
id: 85,
sectionName: 'Consultation',
topics: {
id: 109,
name: 'Was the information correct?',
answers: { answerName: 'NO', topicId: 109 }
}]
My expected output:
[ {id: 85,
sectionName: 'Consultation',
topics: [{
id: 109,
name: 'Was the information correct?',
answers: [{ answerName: 'Yes', topicId: 109 },
{ answerName: 'NO', topicId: 109 }]
}]
} ]
I have also tried JOINING all entites as such:
SELECT sec."id",
sec."name" AS "sectionName",
tp."name" AS topics, ans."name" AS answers
FROM "scorecard" sc
LEFT JOIN "section" sec ON sc."id" = sec."scorecardId"
LEFT JOIN "topic" tp ON tp."sectionId" = sec."id"
LEFT JOIN "answer" ans ON ans."topicId"= tp."id"
WHERE sc."id" = $1
Output is not organized as it should be.
[
{
id: 91,
sectionName: 'Politeness',
topics: 'Was the agent polite with the client?',
answers: 'No'
},
{
id: 91,
sectionName: 'Politeness',
topics: 'Was the agent polite with the client?',
answers: 'Not everytime'
},
{
id: 91,
sectionName: 'Politeness',
topics: 'Was the agent polite with the client?',
answers: 'Yes'
}
]

Answer 1

You can join all four tables to get your result.
SELECT sec."id",
sec."name" AS "sectionName",
tp."name" AS topics, ans."name" AS answers
FROM "scorecard" sc
LEFT JOIN "section" sec ON sc."id" = sec."scorecardId"
LEFT JOIN "topic" tp on tp."sectionId" = sec."id"
LEFT JOIN "answer" ans on ans."topicId"=tp."id"
WHERE sc."id" = 30
Thanks #Luuk for creating the dbfiddle link.
select json_agg(x) AS result
from
(
SELECT sec."id",
sec."name" AS "sectionName",
json_agg(topics) as "topics"
FROM "scorecard" sc
LEFT JOIN "section" sec ON sc."id" = sec."scorecardId"
LEFT JOIN (SELECT tp.id,tp.name,tp."sectionId", json_agg(answers.*) as "answers"
FROM "topic" tp
LEFT JOIN (SELECT ans."name" as "answerName", ans."topicId"
FROM "answer" ans) answers ON answers."topicId" = tp."id"
group by tp.id,tp.name,tp."sectionId"
) topics
ON topics."sectionId" = sec."id"
WHERE sc."id" = 85
group by sec."id", sec."name"
)x
Output:
result
[{"id":85,"sectionName":"Consulation","topics":[{"id":109,"name":"Was the information correct?","sectionId":85,"answers":[{"answerName":"Yes","topicId":109}, <br> {"answerName":"NO","topicId":109}]}]}]
*db<>fiddle here149)

Answer 2

You are missing a JOIN condition to the table topics
SELECT sec."id",
sec."name" AS "sectionName",
topics
FROM "scorecard" sc
LEFT JOIN "section" sec ON sc."id" = sec."scorecardId"
LEFT JOIN (SELECT tp.*
FROM "topic" tp
WHERE tp."sectionId" = sec."id"
(SELECT tp.*
FROM "topic" tp
WHERE tp."sectionId" = sec."id"
)
) as topics ON topics.??? = ??? -- Here you should enter the relation
-- from topics to your section.
WHERE sc."id" = 30
EDIT:
With you (current) input I creates this DBFIDDLE
The output:
[
{
"id": 85,
"sectionName": "Consulation",
"topics": {
"id": 109,
"name": "Was the information correct?",
"sectionId": 85,
"answers": {
"answerName": "Yes",
"topicId": 109
}
}
},
{
"id": 85,
"sectionName": "Consulation",
"topics": {
"id": 109,
"name": "Was the information correct?",
"sectionId": 85,
"answers": {
"answerName": "NO",
"topicId": 109
}
}
}
]